Workers use a crane to lift a jetway, at right, away from a Southwest Airlines airplane after the jetway suffered a mechanical failure on May 13, 2014, at Seattle-Tacoma International Airport. / AP

by Ben Mutzabaugh, USA TODAY

by Ben Mutzabaugh, USA TODAY

Passengers exiting a Southwest Airlines flight in Seattle got an unwanted surprise Tuesday when a jetway leading to the airport terminal gave way.

No one was hurt in the collapse, which dropped the walkway about six feet toward the ground around 10:30 a.m. PT. Passengers were deplaning on a flight arriving from Phoenix at the time of the incident. About half of the plane's passengers already had exited before the jetbridge started to sink at Gate B-14.

Seattle-Tacoma International Airport spokesman Perry Cooper says some passengers were on the jetbridge when it started to give way, but did not know the exact number.

"They were deplaning the aircraft, and as about 60 passengers went through, they started to notice and hear the alarms for the jetbridge, as it started to slowly lower," Cooper tells KING 5 TV of Seattle.

KING 5 says Perry "compared the drop of the jetway to what might happen when you let the air out of a tire."

A mobile stairway was brought to the other side of the plane for the passengers who had not yet deplaned.

The Associated Press says "the cause of the drop was described as a mechanical failure. Thanks to a backup system - a large screw under the jetway that turns as it is raised or lowered - the bridge fell slowly, and those who were on it walked up to the gate, Cooper said."

But as the jetway sank, a canvas weather covering on the platform got stuck on the door of the Boeing 737, pulling the nose of the jet toward the ground, according to AP. Later on Tuesday afternoon, airport crews used a crane to lift the walkway, which allowed the plane to pull back from the gate area.

The plane was taken out of service so it could be inspected for damage.

A Southwest spokeswoman tells The Seattle Times the airline was did all it could to get fliers on their way and that the company was thankful no one was hurt.

Reuters notes that "jetway collapses are rare," but says "the incident is under investigation by airport authorities," according to airport spokeswoman Christina Faine.